Why isn't E a premise booster?

Hi,

I am still struggling with #3. The diagram that proves E is right, also proves why H cannot be 4th, which would trigger:

F (blank)MH and then 3 spots for GP chunk and S,L

If S is 4, why wouldn't it work? Couldn't it be
FMHSGPL or FMHSLGP (in order 1-7).

Thanks!

Thanks, everyone.

Is this a weaken or identify the flaw question with the language: "of the following which one constitutes the strongest objection to the reasoning in the argument"?